11/20 Lecture: Sky Phenomena

[Adrian Cotter]

If you are interested in helping us with finding a new space for next year, and maybe rethinking how we do our lectures and promotion -- please drop me a line in the next few days. We have lots of good ideas just need some extra help to get it all done. 

Thanks,

-- Adrian, aco...@nonsensical.com

NEXT TALK

Sky Phenomena
Guest Speaker: Joe Jordan
7:30pm, Thursday, Nov 20th, 2014
FREE at the Randall Museum, 199 Museum Way, San Francisco, CA

Joe will show pictures of all kinds of atmospheric phenomena, including rainbows, haloes, glories, aurorae, coronae, mirages, and the legendary (but real) “green flash”.   He’ll bring along some hands-on 3-D models (to go along with his descriptions and explanations) that might help us understand what causes some of these things, and where and when to watch for them.

As an added treat, Joe will regale us with information and stories on a recent focus of his — the science, technology and politics, behind clean energy (“sky power to the people” — see his TED talk on it – shown below!) — including the scientific basis for a big public-art sculpture idea.

 

LAST MONTH'S NOTES

Living in the Plate Boundary and Through the Ice Ages

(notes by Joel) Geologist and plate tectonics animator Tanya Atwater spoke to us October 16, 2014. She gave us her presentation called Living in the Plate Boundary and Through the Ice Ages.

The presentation was largely based on diagrammatic animation videos which these notes cannot describe. But you can see them yourself on Atwater’s website  (or you can Google Atwater animations). I apologize that I wasn’t as able to take notes as usual since my eyes were up on the video screen a lot.

The surface of the earth is made of plates floating on (and diving down thousands of miles into) the earth’s molten mantle, which is always flowing.

When you look at the animation of the continents coming into their present formation, India seems to move faster than the rest. This is partly due to the size. Smaller means it can move faster. Of course the speeds are all pretty slow, taking many millions of years. (Speeds are similar to how quickly a fingernail grows, according to Julian’s talk back in July.)

The Himalayas are uplift (crumpling and wrinkling of the plate that pushes the surface up). This is due to the direct-hit crunching of the Indian plate against the plate to its north.

The Pacific Plate is the largest plate, taking up almost 1/3 of the surface of the earth. It’s being dragged past the North American Plate to the NW, scraping against it and at the same time leaving bits behind along the edge.

The area west of North America has been for a long time (until recently) made up of three ocean plates. Ocean plates are formed by spreading mid ocean rifts where mantle magma wells up in the gap. (Continental plates are formed by uplift, by volcanos, by wind and glacial deposits, etc.) The two plates on the east side of the rift zone have flowed under the Americas now (a process called subduction). There’s a tiny bit left of one (Juan de Fuca Plate) in Oregon and North California Coastal waters and a little (of the Farallones Plate) near Central America.

As the rift spreads, the Pacific Plate gets bigger on its east side faster than it moves northwest. That means it grows and seems to come closer while in fact it is moving away. The direction of movement is not directly away, but scraping NW along our coast, pulling our coast out and stretching the North American continent. That’s why the high areas that used to be Utah and Nevada had room to collapse and fall over becoming the basin and range provinces with lots of gaps between high ridges. It’s also why the Gulf of California has opened up.

(more on the website)

http://sfnhs.com/2014/10/24/living-in-the-plate-boundary-and-through-the-ice-ages-2/

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FUTURE TALKS

Nov 20th – Joe Jordan: Sky Phenomena
Dec – No talk. Happy holiday!.

2015

Jan 15th – Lew Stringer: Ice Plants, Mattress Wireweed & Other Onslaughts
Feb 19th – John Wick: Marin Experiments in climate and CO2 sequestration 
Mar 19th – Joel Pomerantz: The Most Extreme Storms Yet